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Vocabulary

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magma chamber- a pocket in which magma collects

pipe- a long tube in the ground that connects the magma chamber to the Earth's surface

vent- an opening where molten rock and gas leave

lava flow- an area covered by lava as it pours out of a vent

crater- a bowl shaped area that may form at the top of a volcano around the volcano's central vent

Silica- a material that is formed from elements oxygen and silicon

Pahoehoe- fast moving, hot lava

aa- cooler, slower moving lava

pyroclastic flow- occurs when explosive eruption hurls out ash, cinders, bombs and gases

active- the term for a live volcano, having the ability to erupt in the near future

dormant- a 'sleeping' volcano, opposite of active, may be able to erupt in the future

extinct- a dead volcano, which is unlikely to erupt again

hot spring- formed when groundwater heated by nearby body of magma rises to the surface and collects in a natural pool

geothermal energy- water heated by magma produces this clean energy

Outline

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T= Volcanic Activity

• How Magma Reaches Earth's Surface

  • lava begins as magma
  • magma forms in asthenosphere
    • materials of asthenosphere under great pressure

• Magma Rises

  • liquid magma is less dense than surrounding solid material, it flow upward into cracks
  • magma floats up until trapped or reaches the surface

• A Volcano Erupts

  • dissolved gases trapped in magma under tremendous pressure
    • as magma rises toward the surface, pressure decreases
      • volcano erupts when opening develops in weak rock
      • once magma reaches surface, becomes lava and gases bubble out

• Inside a Volcano

  • beneath a volcano, magma collects in magma chamber
    • magma moves through a pipe
    • molten rock and gases leave the volcano through a vent

• Characteristics of the Magma

  • the force of a volcanic eruption depends on
    • gas content of magma
    • thickness of magma
    • how much silica the magma contains

• Types of Volcanic Eruptions

  • The silica content in magma helps determine whether the eruption is quiet or explosive

• Quiet Eruptions

  • a volcano erupts if the magma flows easily
    • Quiet Eruptions produce two eruptions=
      • Pahoehoe
        • fast moving, hot lava
        • surface of lava looks like rope- like coils
      • aa
        • when hardens, it forms a rough, jagged chunks of lava

• Explosive Eruptions

  • If thick and sticky, the magma will erupt explosively
    • the pressure will build until it explodes
      • hurtles out=
        • bombs
        • fine sand grains
      • pyroclastic flow

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A diagram of a volcano